Yikes! All of a sudden I see that my thighs are getting kind of bumpy. What can I do to smooth them out again? I'm in my late 30's and never thought I'd get cellulite so young!

Cellulite doesn't discriminate. It can show up on girls in their teens—or younger. That's because, despite what you've heard about cellulite being some mysterious condition linked to "trapped toxins" or poor circulation, cellulite is simply old-fashioned fat. It just looks different because of how it's arranged. (Looking for effective ways to tone up fast? Prevention has smart answers—get a FREE trial + 12 FREE gifts.)

Everyone has strands of connective tissue that separate fat cells into compartments and connect fat to skin. In women, these fibers form a honeycomb-shaped pattern, so any increase of fat tends to bulge out like stuffing in a mattress. You see less cellulite in men because their fibers run horizontally, forming a criss-cross pattern that prevents bulging or dimpling.

Though cellulite can pop up any time, it is true that cellulite does seem to appear out of nowhere and get worse with age. That's because our tissues change. Those strands of connective tissue thicken with age, and our skin gets thinner, making cellulite more noticeable. More importantly, we gain fat with age. The average woman loses 5 lb of muscle and replaces it with about 15 lb of fat every decade of her adult life, says Prevention advisor Wayne Westcott, PhD.

"Because fat is exceptionally soft, it doesn't keep our skin taut like muscle does. It also takes up more space, so it bulges out," he explains.

With the right leg workout plan, you can reduce your cellulite and make your lower body look smoother and firmer, says Westcott. "When we put 16 women ages 26 to 66 on our program for 8 weeks, all of them reported less cellulite in their lower bodies. Seventy percent reported a lot less."

The trick is working all your lower body muscles from every angle, reducing the underlying fat stores and replacing lost muscle tissue to give the area a taut, toned appearance throughout.

Perform 1 set of 10 to 15 repetitions of the following exercises 3 days a week. Lift slowly, counting 2 seconds to lift and 4 seconds to lower. Before starting, warm up thoroughly with walking, stationary cycling, or light calisthenics.

Side to SideMuscles worked: Quadriceps, abductors, adductors, hamstrings, and glutes

Equipment:Dumbbells You can make this basic exercise easier by doing it without any weights. Just keep your hands on your hips. To make it more difficult, hold the dumbbells up at your shoulders while performing the exercise.

1. Stand with your legs shoulder-width apart with your toes pointed out about 45 degrees and your back flat and straight. Hold a dumbbell in each hand and rest them at your hips.

2. Take a giant step to the left and bend your left knee until your thigh is parallel to the floor, keeping your right leg extended. Do not allow your left knee to jut over your toes or your butt to dip below your knee. Pause, then return to the starting position and repeat the motion to the right side without resting.

All-Fours KickbackMuscles worked: Gluteal muscles

Equipment: Ankle weights When doing this exercise, remember not to arch or hunch your back. This will prevent you from putting stress on your back. You can make the exercise easier by doing it without ankle weights. If you don't have ankle weights, do the exercise with a light dumbbell held behind the knee in the crook of your working leg.

1. Wearing ankle weights, get down on your forearms and knees (similar to the hands-and-knees position, but you bend your arms and support your weight on your forearms instead of your hands). Keep your back straight and your head in line with your back so that your eyes are looking down.

2. Keeping your back straight and leg bent, slowly swing your right leg back and lift your right foot toward the ceiling until your thigh is parallel to the ground. Your foot should remain flexed throughout the exercise. Hold for 1 second, then return to the starting position. Do one set with your right leg, then switch and repeat with your left.

Lying Inner-Leg LiftMuscles worked: Inner thighs

Equipment: Ankle weights By working these muscles, you can create a strong, lean line down the insides of your leg. While you're doing this exercise keep your upper body stationary; resist the urge to sway back and forth as you lift and lower. You might also want to do the move without weights first to learn the motion, since it can be somewhat awkward at first.

1. Wearing ankle weights, lie on your left side, resting your head on your upper arm, and place your right hand on the floor in front of your chest for support. Bend the knee of your top leg, placing the foot of that leg in front of your other knee. Your bottom leg should be fully extended.

2. Slowly raise your bottom leg as high as is comfortably possible. Hold for 1 second, then slowly lower. Do one set with your left leg, then switch and repeat with your right.

Equipment: Ankle weights Wearing ankle weights, stand with your feet shoulder-width apart, with your hands on your hips, your elbows out to the sides, and your toes slightly pointed out. Remember to keep your head straight and your eyes facing forward. If you want to push yourself a bit, hold a light dumbbell in each hand as you do the moves.

1. Slowly bend at the knees and squat back as though moving your butt down toward an imaginary chair. Keep your back flat, and don't allow your knees to jut over your toes. Stop when your thighs are just about parallel to the floor; don't go any lower.

2. Pause, then straighten your legs, lifting your left leg off the floor and out to the side as you stand. Pause again, then return to the starting position. Repeat, lifting your right leg to the side this time. Alternate legs throughout the exercise.

When going through these moves, keep your back flat on the floor; do not arch your lower back or twist your torso. If balance is a problem, lie next to a chair and hold on to one of its legs for support.

1. Loosely tie an exercise band around your ankles and lie on your back with your arms down at your sides. Extend both legs straight up directly above your hips, with your feet spread wide enough that the exercise band is slightly taut. Flex your feet.

2. Slowly open your legs as far as you can. When the tension becomes too great to pull any farther, pause, then slowly close your legs back to the starting position.

One-Legged LungeMuscles worked:Glutes, quadriceps, and hamstrings

Equipment: A sturdy chair or bench Since this is a bit of an advanced exercise, practice doing regular lunges to get comfortable with the movement before you start. To make this move even more challenging, hold dumbbells down at your sides.

1. Stand about 2 feet in front of a sturdy chair or bench with your back to it. Bend your left knee and extend your left leg behind you, putting the top of your left foot on the seat of the chair. Keep your back straight, your head aligned with your spine, and your eyes facing forward.

2. Slowly bend your right knee until it is parallel to the floor. Do not allow your right knee to jut over your toes. Pause, then rise back to the starting position. Do one set with your right leg, then switch and repeat with your left.